US2930909A

US2930909A - Radioactive battery with solid dielectric spacers and method of manufacture

Info

Publication number: US2930909A
Application number: US470566A
Authority: US
Inventors: Harry C Lieb
Original assignee: Leesona Corp
Current assignee: Leesona Corp
Priority date: 1954-11-23
Filing date: 1954-11-23
Publication date: 1960-03-29
Anticipated expiration: 1977-03-29

Description

March 29, 1960 mung?D CTIVE `BATT ACERS AND Filed INVENTOR. HARRY C. LIEB.

ATTURNEY 2,930,909 Y Y RADIoAcTivE BATTERY WITH SOLID DIELEC- TRIC SPACERS AND METHOD F MANUFAC- Harry C. Lieb, Rockville Centre, N.Y., assgnor to Leesona Corporation, a corporation of Massachusetts t Application November z3, 1954, serial No. 410,566

1s claims. (cl. 31o- 3) The present invention relates to the generation ofielectn'cal energy and more particularly relates to anapp'aratus for utilizing the electrical energy of nuclear reactions and the method of manufacturing such apparatus.v

Radioactive materials emit alpha-particles or beta-particles, or both, in the course of their nuclear reactions. The alpha-particles are positively charged and the betaparticles are negatively charged and the energies of these particles may be several million electron volts. In theY past devices have been made to utilize directly the elec- A. 4United States Patent `O 2,930,909 Patented Mar. 29, 1960 an electron collector. A lead is connected to the radioactive material and becomes the positive terminal of the trical energy of these particles by placing a collector electrode or electrodes adjacent a supply of radioactive material to collect the charged particles and to thereby build up a potential between the radioactive material and said collectorelectrode. These devices have been unreliable and ineilicient in performance, expensive, relatively large in size, easily broken, and constitute a hazard to the health of personnel who malte oruse them.

It is accordingly onepobjectof the present invention to provide a compact and elllcient device for utilizing directly the electrical energy from a nuclear reaction.; L A

Anotherobject of the? present invention is to provide a device for utilizing directly the electrical energy of nuclear reactions wherein the electrons emit-ted' from a radioactive material are collected in a highly eicient manner.

vAnother object of the present invention is to provide a device ffor utilizing directly the electrical energy of nuclear reactions that is dependable and which can be produced in large quantities at reasonable cost.

Another object of the present invention is to provide Ya device for utilizing directly the electrical energy from a nuclear reaction that is rugged and which willV continue to function under extreme conditions of and/or shock.

Another object of the present invention is to provide a device for utilizing directly the electrical energy from a nuclear reaction that can be safely manufactured and which will not endanger the health of personnel using it.

Other objects of the invention will inpart be `obvious and will in part appear'hereinafter.

The invention accordingly comprises the apparatus possessing the construction, combination'of elements and arrangement of parts4 which -arefexemp'liedfin the following detailed disclosure, a'ndl-the scope of the application of which will beindicated in the claims.

VFor a fuller `understanding of the nature and objects of the invention, reference should be had to the following `detailed description taken in connection with the accompanying drawing which is a sectional view of a preferred embodiment of the present invention.

The device of the present invention for directly utilizing the electrical energy olf-nuclear reactions will 'be Vreferred to hereinafter as a radioactive battery.- The present battery comprises'a supply of radioactive-material, preferably strontium 90, that is a beta emitter-en-` cased in a solid dielectric which inturn is enclosed temperature battery and a terminal is provided on the collector element which becomes the negative battery terminal.

The method of the present invention includes the stepsV of deposit-ing the radioactive material in the unit in solution and evaporating the solvent and bonding the dielectric material together around the radioactive mate` rial.

Referring now to the drawing,one embodiment of the. radioactive battery of the present invention comprises a thin walled cup 10 preferably stamped from copper foil. The inner surface of cup 10 is provided with a thin coating of radioactive material which preferably includesy Cupl 10 has a substantially cylindrical side Wall and a spherical bottom wall and is mounted ina solid dielectric element strontium in the form of strontium chloride.

12,'preferably polystyrene, `that has the same configuration as cup 10. The wall thickness of dielectric element 12 is substantially uniform throughout the element and itsside walls extend above the top of cup 10 a distanceslightly greater than the thickness of said dielectric.` A second solid dielectric element 14, also preferably polys-tyrene, is nested inside of cup 10 and dielectric element 12. Dielectric element 14 is also generallyv cup shape and conforms to the inside of cup 10 and element 12. The wall thickness of dielectric element 14 is substantially equal to the wall thickness of element 12 and its outside diameter is such that it'ts snugly inside of cup 10 and element 12. The uppermost end of element 14 is provided with an outwardlyextending llange or lip 16 that extends outwardly over the top of said di-n The two dielectric elements 12 and electric element 12. 14 are fused together along their contiguous side walls above cup 10 vand along the top of element 12. and thel under surface of flange 16 to seal the contained radioactive material therebetweenv against any possibility of escape.

A collector plug 18, preferably formed of brass, snugly ts inside of `dielectric element 14 and is provided at its uppermost end with an outwardly extending flange 20 that engages the uppermost surface of dielectric flange 16. Aligned

openings

22 and 24 are provided in

ilanges

20 and 16 respectively in substantial alignment with the side i, wall of cup 12 and

mating channels

26 and 28 are aligned.

collector plug 18 `and Wire 30 are mounted in a collec. tor case 36, preferably brass, that is generally cylin-` drical in shape and provided with'ra cup-shaped recess that conforms to the outer surface of dielectric lelement 12, dielectric flange 16V and collector plug llange 20. Collector plug llange Ztl is bevelled along its upper edge 4as shown at38 and the upper edge of case 36 is rolled` over the bevelto secure the unit together. The joint between case 36 and flange 20 not only secures said case and plug together mechanically but also connects thesev two elements electrically so thatftogether they function.

as a collector electrode. In addition to the mechanical connection between case 36 and llange 20 the joint `therebetween, and also between insulation 32 and flange 20 is sealed witha layer of thermo-setting plastic 40 that ad-y vantageously Vcan'rbe epozyresin. A terminal 42..l is, "-'formedon the base of case 36 andtogether with Wire" 3 30* provides the means for connecting the battery of thepresent invention to an electrical circuit.

The above described apparatus functions in the following` manner. Electrons emitted by the radioactive material'carried by cup10 pass through dielectric materialVV 12'and 14 and into collector plug 1Sand collector case 36`giving those two units a negative charge. The cup shape of emitter electrode and the radioactive materialv carried thereby is highly eiiicient andpermits a much higher percentage of the electrons toreach a collector. electrode than has been possible in radioactive batteries heretofore known. At the same time the loss of the electron from the radioactive material and cup 10 leaves these elements with a positive charge. Therefore, when terminal 42 and wire 30 are connected, electrical energy. will 'ow from said terminal 42 to said wire 30.' TheA thickness of dielectric members 12 and* 14 is such thatV the electrons emitted from the radioactive material can pass. therethrough and enter either collector plug 18 or collector case 36. However, theymust be thick enough to prevent backscattered secondary electrons from either said'collector plug or case from passing back therethrough to the cup 10. The wall thickness of collector, case 36H is such that all electrons that pass through dielectric material 12 will be absorbed by said case thus preventingr any. of them from passing completely out of the radioactive. battery. Polymonoehlorotrifluorethylene, the material employed to insulate wire 30 isl preferred because itrdoes not absorb moisture and will not transmit moisture vapor. However, this materialV is deteriorated by beta radiation and therefore said insulation terminates adjacentv the upper end of dielectric material12.V Tjhis. distance is sufficiently remote from the radioactive -material which extends only part way. up the` wall of j cup 10, that substantially no beta particlesy cany penetrate dil

electric material

12 and 14 to reach it.

The above described radioactive battery is preferably. manufactured in the following manner. Collector case '36 and collector plug 18 may be cast or machined, di:

electric elements

12 and 14 are preferably moulded to shape and electrode cup 10' is preferably formed by a.

drawing operation. Electrode cup 10 is iirstrassembled inthe outer dielectricmember 12' and the assembledcup and dielectric is inserted in collector case 36. Following this.. assembly, the radioactive material is introducedginto, cup 10in solution. When strontium 90 is employedvas the radioactive material, strontium chloride inacid solu- -tion is introduced into said cup. Very accurate control ofthe quantity of radioactive material deposited. is` possible by this method inasmuch as the concentration, of, the solution can be determined with great accuracy and a,dilute solution is preferably introduced into, cup4 10. by means of a pipette. The unit as thus far assembled. and. containing the radioactive solution in cup 10 is thensub.- jccted` tol a drying operation to evaporate the. solvent to leave a thin deposit of radioactive material ontheil'men surface of cup 10. Obviously heatand/ or a vacuum can be used in this evaporating step.

Dielectric 14 and collector plug 18 are nextassembled, Wire 30 is passed through aligned openings 22 and24. and the dielectric and collector plug assembly is then positioned in collector case 36 with the swaged end 34 offwire 30 against the radioactive material and theinner surface of cup 10. The entire assembly. is4 thenheatedr to a. temperature above the fusion temperature of, di-

electric elements

12 and 14 and pressure is applied to` plug 1S to cause the two dielectric elements to conform4 elementV 14 to thereby effectively seal the radioactive,

material between said dielectric elements. Followingfthe,

heatinggand. pressure applying and bonding; steps, the;

aaseeoa.

i unit is cooled and the upper edge of collector cup 36 is rolled inwardly to mechanically lock the assembly together and to give a good electrical connection between the two collector elements. A small quantity of thermosetting plastic is deposited in the upper end of the newly formed battery in the receptacle formed by the inturned upper edge of case 36 and the unit is subjected to enough heat to cause the plastic to polymerize and to thereby provide an` additional seal to the unit.

A specific example of a device including the features set forth above was constructed with the components thereofy having the following proportions:

Diameter of copper emitter cup inches .298 Wall thickness of emitter cup do v .00067 Height of emitter cup do .250 Wall thickness of brass collector case do .040 Thickness of polystyrene dielectric do .010-.060 Sr C12 radioactive material ..millicuries 1 I The, batteryv thus constructed used the kinetic energy 'o f, the. beta, particles emitted from the radioactive material to buildl up to an equilibrium voltage of approximately 75500 volts atY 4x1012 amperes. The amperes will! increase in a linear fashion as the quantity of radio-l active material is increased up to about 4 me. The amperes f all off somewhat after 4 mc. of radioactive'ma.- ter-ial, is exceeded due to secondary radiation and self absorption.

The radioactive battery and the method by which it is manufactured hasv been described hereinabove as employing an emitter cup or electrode to hold and positiony the radioactive material. It should be pointed out, however, that in some instances'the emitter cup can be (lis,-

pensed. with and the radioactive material deposited di.

tance fromthe outside thereof, an electrically conductive'v collector pluggsecured to said case and substantially'uniformly spaced said predetermined distance fromthe inside.

ofsaid material,y said case and plug forming a.collector. electrodethe space between said material and said case` and between said material and said plug being illed'withV afsolidVV dielectric, said solid dielectric being'in closexc0ntac twith said radioactive material, the inner surface ofy said,v collectort case; and said collector plug, and' a lead. insulatedl fromV said collector connectedto saidmaterial'. and extendingtherefrom' to outside of said case, said'predetermined distance beingsuch that chargedparticles.l can pass from said material through said dielectric material to said collectory electrode bjutbackscatteredsecondary electrons will b e absorbed .by said dielectric in theeventthey are reflected by said,collector-electrode.

2. A radioactivebattery comprising a cup-shaped emit-- terelectrode, having a substantially cylindrical' side wall andisubstantially semi-spherical bottom wall, a coatingof. radioactive material on said emitter electrode, said-v coating; covering" said bottom wall and extending part way up said sidewall, an electrically conducting collector-- case-.enclosing said emitter and spaced a substantiallyuniform predetermined' distance from the outside thereof,r an:- electricallyconductive collector plug secured to said case -and..substantially;V uniformly spaced saidl predetermined? ,emitter and said case and between said emitter and said plug being iilled with a solid dielectric, said solid dielectric being in close contact with said radioactive material, emitter electrode, the inner surface of said collector case and said collector plug, and a lead insulated from said collector connected to said emitter and `extending therefrom to outside of said case, said predetermined distance being such that charged particles can passV from said emitter through said dielectric material to said collector electrode but backscattered secondary electrons will. be absorbed by said dielectric in the event they are reflected by said collector electrode.

3; A radioactive battery comprising a cup-shaped radioa solid dielectric, said solid dielectricbeing in close con tact with said radioactive material, the inner surfaceV of said collector case and said collector plug, and a leadv insulated from said collector connected to said material and extending therefromto outside of said case, said predetermined distance being such that charged particles can pass from said material throughv said dielectric material to said collector electrode but backscattered secondary electrons Will be` absorbed by said dielectric in the event they are reflected by said collector electrode, said collector case having walls capable of preventing any charged particles Vfrom passing therethrough.

V4. A radioactive battery comprising a cup-shaped emit- 1 ter `electrode having a substantially cylindrical side Wall and'substantially semi-spherical bottom wall, a coating of radioactive. material on said emitter electrode, ,said coating `covering said bottom` Wall and extending part way up said side wall, an electrically conducting collector case enclosing said emitter and spaced a substantially uniform predetermined distance from the outside thereof, an electrically conductive collector plug secured to said case and substantially uniformly spaced said predetermined distance from the inside of said emitter, said case and plug forming a collector electrode, lthe space between said emitterand said case and between said emitter and said plug'being lilled with` a solid dielectric, said solid dielectricbeing in. close contact with saidra'dioactive material, emitter electrode, the vinner surfacetof said collector v case and said collector plug, and a leadV insulated from `said collector connected to said emitter and extending therefrom to outside of said case, said predetermined distance being such that charged particles can-pass from said emitter 'through said dielectric material to said collector electrode but backscattered secondary electrons `will be absorbed by said dielectric in the event they are reflected byrsaid collector electrode, said collector case having walls capable of preventing any charged particles from passing therethrough; A l' r5. radioactive battery comprising a cup-shaped radioactive` material having a substantially cylindrical side wall and substantially semispherical bottom Wall, anv

electrically conducting collector case enclosing said material and' spacedl a substantially uniformpredetermined distance from the outside thereof, an electrically conductive collector plug secured to said case and substantially uniformly spaced said predetermined distance from the inside` of said material, said case and plug forming a collector electrode, the space between said material and said case andbetween said material and said plug being filled` with a solid dielectric, and a lead insulated from A saiducollector'connected to said material and extending therefrom to4 outside `of said case, said dielectric Ybeing Y. radioactivematerial on said emitter electrode, said coatl bonded together around said material and being in close contact with said material, the inner surface of said collector case and said collector plug, said predetermined distance being such that charged particles can pass from said material throughY said dielectric material to said collector electrode but backscattered secondary electrons will be absorbed by said dielectric inthe event they are reected by said collector electrode. Y

6. A radioactive battery comprising a cup-shaped emitter electrode having a substantially cylindrical side wall and substantially semi-spherical bottom wall, a coating of radioactive material on said emitter electrode, said coating covering said bottom wall and extending part way up said side wall, an electrically conducting collector case enclosing said emitter and spaced a substantially uniform predetermined distance from the outside thereof, an electrically conductive collector plug secured to said case and substantially uniformly spaced said predetermined distance from the inside of said emitter, said case and plug forming a collector electrode, the space between s aid emitter and said case and between saidl emitter and said plug being lilled with a solid dielectric, and a lead insulated from said collector connected to said emitter i and extending therefrom to outside of said case, said dielectric being bonded together around said emitter and being in close contact with said radioactive material, emitter electrode, the inner surface of said collector case andsaidcollector plug, said predetermined distance being such that charged particles can pass from said emitterI spaced a substantially uniform predetermined distance vfrom the outside thereof, an electrically conductive collector plug secured to said case and substantially uniformly spaced said predetermined distance from the inside t of Vsaid material, said case and plug forming a collector electrode, the space ,between said material and said case and between said material and said plug being filled with asolid dielectric, and a lead insulated from said collector connected to said material and extending therefrom t0 outside of said case, said dielectric being bonded together aroundV said material and being in close contact with said material, the inner surface of said collector case and said collector plug, said predetermined distance being such that charged particles can pass from said emitter through said dielectric material to said collector electrode but backscattered secondary electrons will be absorbed by said dielectric in the event they are reected by said collector electrode, said collector case having walls capable of preventing any charged particles from passing therethrough.

` `8.,A radioactive battery comprising a cup-shaped emitter electrode having a substantially cylindrical side Wall and substantially semi-spherical bottom Wall, a coating of ,t ing covering said bottom wall and extending part way up said side Wall, anelectrically conducting collector case enclosing said emitter and spaced a substantially uniform predetermined distance from the outside thereof, an electrically conductive collector plug secured to said case and substantially uniformly spaced said predetermined. distance Vfrom the inside 'of said emitter, said case and plug forming a collector electrode, the space between said ernitter, and said case and between said emitter and saidV plug being lled with a solid dielectric, and a lead insulated from said collector connected to said emitter and extending therefrom to outside of said case, said dielectric being bondedttogether around said emitter and being in close contact with said radioactive material, emitter electrode, the inner surface of said collector case andi said collector plug, said predeterminedv distance being such that charged particles can pass from said emitter through said dielectric material to said collector electrode but backscattered secondary electrons will he absorbed by said dielectric in the event they are reflected by said collector electrode, said collector case having walls capable of preventing any charged particles from passing therethrough.

9. A radioactive battery comprising a radioactive beta emitter having a cup-like shape having a substantially cylindrical side wall and substantially semispherical bottom wall, an electrically conducting collector case enclosingsaid emitter and space a substantially uniform predetermined distance from the outside thereof, an electrically conductive collector plug secured to said case and substantially uniformly spaced said predetermined distance' from the inside of said emitter, said case and plug forming a collector electrode, the space between said emitter and said case and between said emitter `and said plug being iilled with a solid dielectric, said solid dielectric-v beingin close contact with said beta emitter, thev innersurf'ace of said collector case and said collector plug, and a lead insulated from said collector connected to s aid emitter and extending therefrom to outside of said case, said predetermined distance being such that beta particles can pass from said emitter through said dielectric material to said collector electrode but backseattered secondary electrons will be absorbed by said dielectric in the event they are reflected by said collector electrode.

l0. A radioactive battery comprising a cup-shaped emitter electrode having a substantially cylindrical side wall and substantially semi-spherical bottom wall, a coating of radioactive beta emitting material on said emitter electrode, said coating covering said bottom wall and extending part way up said side wall, an electrically conducting collector caseenclosing said emitter and spaced a substantially uniform predetermined distance from the outside thereof, an electrically conductive collector plug secured to said case and substantially uniformly spaced said predetermined distance from the inside of said emitter, said case and plug forming a collector electrode, the space between said emitter and said case and between said emitter and said plug being filled with a solid dielectric, said solid dielectric being in close contact with said beta emitter, emitter electrode, the inner surface of said collector case and said collector plug, and a lead insulated from saidvcollector connected to said emitter and extending therefrom to outside of said case, said predetermined distance being such that beta particles can pass from said emitter through said dielectric material to said collector electrode buttbackscattered secondary electrons will be absorbed by said dielectric inthe event they are reflected by said collector electrode.

1l. A radioactive battery comprising a radioactivebeta emitter having a cup-like shape having a substantially cylindrical side Wall and substantially semi-spherical bottom wall, an electrically `conducting collector case enclosing said emitter and spaced a substantially uniform predetermined distance from the outside thereof, an electrically conductive collector plug secured to said case and substantially uniformly spaced said predetermined distance from 'the inside of said emitter, said case and plug formingA a .collector electrode, the space between said emitter and said case and between said emitter and said plug being filled with a solid dielectric, said solid dielectric being in close contact with said beta emitter, the inner surface of said collector case and said collector plug, and a lead insulated from said collector connected to said emitter and extending therefrom to outside of said case, said dielectric being bonded together around said emitter, said predetermined distance being such that beta particles can p-assj from` said emitter through said dielectric materi'al to said collector electrode but backscattered secondary electrons will be absorbed by said dielectric in the event they are reflected by said collector electrode.

' 12. A radioactive battery comprising a cup-shaped emitter electrode having a substantially cylindrical side 5k Wall and substantially semi-spherical bottom wall, a coating of radioactive beta emitting material on said emitter electrode, said coating covering said bottom wall and extending part way up said side wall, an electrically conducting collector case enclosing said emitter and spaced a substantially uniform predetermined distance from the outside thereof, an electrically conductive collector plug secured to said case and substantially uniformly spaced said predetermined distance from the inside of said emitter, said case and plug forming a collector electrode, the space between said emitter and said case and between said emitter and said plug being filled with a solid dielectric, said solid dielectric being in close contact with said beta emitter, emitter electrode, the inner surface of said collector case and said collector plug, and a lead insulated from said collector connected to said emitter and extending therefrom to outside of said case, said dielectric being bonded together around said emitter, said predetermined distance being such that beta particles can pass from said emitter through said dielectric material to said collector electrode but backscattered secondary electrons will be absorbed by said dielectric in the event they are reflected by said collector electrode.

13. The method of manufacturing a radioactive battery including the steps of placing a predetermined quantity of a solution containing a radioactive material on a thermoplastic battery element, evaporating the solvent to deposit said radioactive material on the surface of said element,

positioning a second'thermo-plastic element over said.

` radioactive material, heating said material and elements above the fusion temperature of said elements, and pressing said elements together to bring them into close contact with said material and to bond them to each other around said material.

14. The method of manufacturing a radioactive battery 40 including the steps of placing a predetermined quantity of a solution .containing a radioactive material in a cupshaped thermo-plastic battery element, evaporating the solvent to deposit said radioactive material on the surface of said element, positioning a second cup-shaped thermoplastic element in said rst element over said radioactive material, heating said material and elements above the fusion temperature of said elements, and pressing said elements together to bring them into close contact with said material and to bond them to each other around said material.

15. The method of manufacturing a radioactive battery including the steps of positioning a cup-shaped emitter electrode in a cup-shaped thermo-plastic element, placing a predetermined quantity of a solution containing aradio-v active material in said electrode, evaporating the solvent to deposit said radioactive material on the surface of said electrode, positioning a second cup-shaped thermo-plastic element in said electrode and first mentioned element,l

heating said material and elements above the fusion temperature of said elements, and pressing said elements together to bring them into close contact with said electrode and material and to bondthem to each other around said electrode.

References Cited in the le of this patent OTHER REFERENCES Radioisotopic High-Potential Low Current Sources,` published by John H. Coleman; Nucleonics (December.

1953), v ol II, No; 12, pp. 42-45, McGraw-Hill Pub lshine C9,

Claims

1. A RADIOACTIVE BATTERY COMPRISING A CUP-SHAPED RADIOACTIVE MATERIAL HAVING A SUBSTANTIALLY CYLINDRICAL SIDE WALL AND SUBSTANTIALLY SEMISPHERICAL BOTTOM WALL, AN ELECTRICALLY CONDUCTING COLLECTOR CASE ENCLOSING SAID MATERIAL AND SPACED A SUBSTANTIALLY UNIFORM PREDETERMINED DISTANCE FROM THE OUTSIDE THEREOF, AN ELECTRICALLY CONDUCTIVE COLLECTOR PLUG SECURED TO SAID CASE AND SUBSTANTIALLY UNIFORMLY SPACED SAID PREDETERMINED DISTANCE FROM THE INSIDE OF SAID MATERIAL, SAID CASE AND PLUG FORMING A COLLECTOR ELECTRODE, THE SPACE BETWEEN SAID MATERIAL AND SAID CASE AND BETWEEN SAID MATERIAL AND SAID PLUG BEING FILLED WITH A SOLID DIELECTRIC, SAID SOLID DIELECTRIC BEING IN CLOSE CONTACT WITH SAID RADIOACTIVE MATERIAL, THE INNER SURFACE OF SAID COLLECTOR CASE AND SAID COLLECTOR PLUG, AND A LEAD INSULATED FROM SAID COLLECTOR CONNECTED TO SAID MATERIAL AND EXTENDING THEREFROM TO OUTSIDE OF SAID CASE, SAID PREDETERMINED DISTANCE BEING SUCH THAT CHARGED PARTICLES CAN PASS FROM SAID MATERIAL THROUGH SAID DIELECTRIC MATERIAL TO SAID COLLECTOR ELECTRODE BUT BACKSCATTERED SECONDARY ELECTRONS WILL BE ABSORBED BY SAID DIELECTRIC IN THE EVENT THEY ARE REFLECTED BY SAID COLLECTOR ELECTRODE.